Electroplating of nickel



Patented Oct, 5, 1954 ELECTROPLATING OF NICKEL Henry Brown, Detroit, Mich., assignor, by mesne assigmnents, to The Udylite Corporation, Detroit, Mich, a corporation of Delaware No Drawing. Application August 5, 1950, Serial No. 177,980

21 Claims.

My invention relates to improvements in the electrodeposition of nickel from aqueous acidic baths. It is particularly concerned with the utilization of certain addition agents for the purpose of decreasing grain size and increasing the luster of the nickel plate or deposit, and it is especially concerned with the production of electrodeposits of brilliant, highly lustrous, ductile nickel plates.

I have discovered that the grain size of electrodeposits may be decreased and the luster of the nickel deposit increased, all in an effective manner, by the utilization of certain bath-soluble organic compounds, specifically, certain esters of unsaturated aliphatic monocarboxylic acids, the unsaturation of which acids is due solely to double bonds. Particularly satisfactory are the methyl and ethyl esters of unsaturated aliphatic monocarboxylic acids containing from 3 to 4 carbon atoms although excellent results are also obtained through the utilization of certain alkoxy alkyl esters of such unsaturated monocarboxylic acids. Some of these esters may be represented by the general formula:

is the acyl radical of an unsaturated aliphatic monocarboxylic acid containing not more than 6 carbon atoms and the unsaturation of which is due solely to double bonds, and X is a member selected from the group consisting of methyl, ethyl, 2-methoxyethyl, 2-ethoxyethyl, phenyl, and 2-phenoxyethyl.

The following Table I lists a number of representative esters whose use falls within the scope of my present invention. It will be understood that the solubility of such esters varies. For effective results they should be soluble in the aqueous acidic nickel plating bath to the extent of the order of at least about 0.15 gram per liter. In general, it is unnecessary to utilize the even more soluble ones of such esters in amounts greater than approximately 3 grams per liter. In

2 Table I Esters of Unsaturated Monocarboxylic Acids g 2-(5methoxyethoxy) ethyl acrylate. Methyl ester of buten-S-oic acid. Methyl ester of vinylacetic acld Phenyl acrylate Z-phcnoxy ethyl acrylate I have also discovered that if there is utilized in the plating bath, in conjunction with the aforesaid esters, a small proportion of a brightener of the organic sulfonic, sulfonamide or sulfonimide type, exceptionally brilliant, highly lustrous, ductile nickel plates having excellent adherence characteristics to the base metal are obtained. While it has heretofore been known to utilize brighteners of the aforesaid organic sulfonic, sulfonamide and sulfonimide types, as is disclosed in part, for example, in my prior Patents Nos- 2,191,813 and 2,466,677, it should be understood that I do not claim any invention here in the utilization of such known brighteners per se. So far as this phase of my invention is concerned, a coaction takes place in the cathode film, the exact nature of which is unknown, involving the ester of the unsaturated aliphatic monocarboxylic acid and the organic sulfur-containing brightener, which produces the unusual and highly important results which are brought about in accordance with this aspect of my invention. In this connection, it may be noted that the utilization of the esters of the unsaturated aliphatic monocarboxylic acids alone or the utilization of the organic sulfur-containing brighteners alone gives no indication of the remarkably enhanced results which occur when both types of compounds are present in the bath, particularly when utilized in their optimum concentrations. Typical examples of organic sulfur-containing brighteners which may be utilized in accordance with my present invention, in conjunction with the esters of unsaturated aliphatic monocarboxylic acids, are disclosed in my prior Patents Nos. 2,191,813 and 2,466,677 and in Table II.

Table II as I have indicated above, a brilliant mirror-like deposit is obtained even over a matte surface. Optimum In the usual case, the compounds of Table I slflfur'olmtaming Bl'ighteners fg fi tend to be consumed at a faster rate during the electroplating process than the compounds of L Benzene sulfonamide Table II. The compounds of Table I, n general, 2. Toluene slullifigamldes (oand p-) 0.1-2 have a faster rate of reduction at the mckel cath- 3. o-Benzoy s mide 0.1-2 N Benzoylbemene sulfonimiden O'H ode with respect to the mckel ion, whereas the g. p-golucuoesulfonchioramidgun H compounds of Table II, 1n general, have a slower 1') rom enzene S11 ORB-m1 e..- ashlar obemoylsulfimide 0'14 10 rate, that is, the mckel 1011 is reduced pieferen g. 1dl.%1dehtld(l) genzenesullffouamige 0.1-1 tially 1n the latter case.

. ome y enzene su onami e 0.1-6 y 10. Benzene sulfonamide m-carboxylic amide. 0.1-3 h aqueous nlclfel platlng baths may 9 A1d h u ebenums m ide -g various types but, 1n all cases, they are acidic 13. Memo, benzene sulfommideibh in character. The preferred baths are those of 14. Hydroxymethylbenzenesullonamid 0.1-2 the Watts type or modifications thereof. The

13; X q lggfigi i3; nickel salts may comprise nickel chloride, nickel Bsgizenebsulfonic a 1d 1 sulfate, nickel fluoborate, nickel sulfamate, or

. 1')- rom QDZEHOS 01110810 Bemaldehyde Sammie acids (0, m H other nickel salts or mixtures of any two or more 31 11 1 1 11 511110 suilfonir ac(id.... at i-g of sa1d mckel salts, preferably in comunction ap B cnes 01108.61 5 H101'10-, l- 811 1'1- Benzene sulfohydmmmic acid n with buffer materlals as, for example, bone acid. 2. 01 11 lienzlcfenesulioiiilc ac1d-. 1 12 I prefer to utilize borlc acid 1n the bath as it p eny SL1 01110 80 s e 25. m-Diphenyl benzene Home a i H 1s, m gene1al, the best cathode film buffer. Other Z-flfloro-fi-sglkg g zalcle hyde.. -5 buffers of acidic character may, however, be emfi 'ffiifii i ifif if 4i, ploy d as. f r xamp f rm d. fi b r acid, and the like, and such may be used either It will be understood that said sulfonic g of or g gg p fi z fii brighteners may be utilized in their acid form op i 5 b 1 30 or in the form of salts as, for example, nickel, bone acld Its f S on d e a me sodium, potassium or other salts. Especially satgrams per hter; especlany m baths opelated at isfactory, for use in the practice of my present 30 somewhat f D The baths y invention, are the compounds of Table II correalso contam v n pp n agents ch sponding to numbers 1, 2, 3, 18, 19, 21 and 28, as antipitting agents and the like. In Table III,

the latter particularly in the form of their nickel I list preferred embodiments of bath compositions.

Table III Bath NlSO .fiHzO N1C1z.6H2O Ni(BF4)2 HaBOa Tempera- Optimum No. grams/liter grams/liter grams/liter grams/liter ture, 0. pH Addition Agents 1 250 to 300 to 75 35 to 40... to 651. 2.8 to 4.8--.. Z-methowethyl acrylatc, 2 grams/liter.

2 75 to 100 35 to 40...- 40 to 65...- 2.8 to 4.8--.. 2-methoxyethyl acrylate, 2 grams/liter, plus benzene sulionamide, 1 to 3 grams/liter; o-benzoyl sulfimide, 0.1 to 2 grams/liter.

3 200 to 250 30 to 60 7 to 15 35 to 40.... 40 to 50..-- 2.8 to 4.8.-.. Ethyl acrylate, 2 grams/liter.

4 300 40 40 40 to 50..- 2.8 to 4.8 Methyl acrylatc, 2gmms/liter.

6 250 to 300 35 to 75 36 to 40...- 40 to 50... 2.8 to 4.8 Methyl acrylate, 2 grams/liter plus 0.1 gram] liter o-benzoyl sulflmide and/or 2 grams/liter benzene sulionamlde.

6 0 to 35 150 to 300.... 0 to 40..... 40 to 50.... 2.8 to 5.0-... Methyl acrylote, 2 grams/liter.

7 Oto 35 150 to 300.... 0 to 40...-- 40 to 50..-. 2.8 to 5.0. Z-methoxyethyl acrylate, 2 grams/liter;

o-benzoyl sulfimide, 0.1-.3 gram/liter.

salts. Where the term sulfonic acids is used herein and in the claims, it will be understood that the salts thereof are likewise included.

The compounds of Table II produce bright and mirror-like deposits on buffed metals such as buffed brass. However, at least in the ordinary case, they do not accomplish the same results on steel polished with 180 emery or on matte (but unburnt) copper plate of 0.0003-0.0005 thickness but, rather, generally yield plates of somewhat dull and gray appearance in these cases. The compounds of Table I, in the usual case, give a difierent type of plate than that produced by the compounds of Table II. The plates produced with the compounds of Table I are generally cloudy and milky on buffed or matte metal. The rate of improvement of luster of the base or basis metal is much more rapid with the compounds of Table I, per se, than with the compounds of Table 11, per se. If, however, the two different types of compounds represented in Tables I and II are used together in the baths,

As I have indicated previously, the concentration of the Table I compounds in the bath may range from about 0.2 gram to about 3 grams per liter. For optimum results, a range of about 0.6 to 2 grams per liter usually is approximately correct. In certain, and perhaps most, cases, these concentrations are close to saturation for the particular esters utilized. Continuous filtration and the use of surface-active agents to prevent pitting tend to aid in solubilizing at least to a certain extent the compounds of Table I and such procedures are, therefore, recommended in at least most cases. Where the esters of Table Iwhich are selected for use have an appreciable vapor pressure at the temperature at which the bath is operated, suitable ventilation should be provided.

The baths can be operated at temperatures ranging from about room temperature to almost boiling but, in general, the preferred temperature is in the range of about 40 degrees C. to 65 degrees C. Where the bath are operated at somewhat elevated temperatures, it will beunderstood that the esters of the unsaturated Ell:- phatic monocarboxylic acids selected should be those which are stable at the bath temperatures, and, in general, it will be advisable to employ esters which do not boil below about 80 degrees C.- and which, preferably, have still higher boiling points. In .general, the baths can be operated at pH values ranging from about 2 to about'5.5 but, in the ordinary case, the preferred pH values are from 3.0 to 4.8. The cathode current density ranges are quite variable, a range of about 5 to several hundred amperes per square foot being utilizable, the optimum depending upon agitation, temperature, and concentrationand type of nickel salts utilized in the bath. A good working range is about to about 80 amperes per square foot. Most of the compounds of Table I function optimumly at pH values of about 3.8 to 4.5 and at bath temperatures of about 45 degrees C. to 60 degrees C. Generally speaking, the lower the temperature of the bath, the higher the pH value at which the bath should be op-y erated for obtaining optimum results.

It should be understood that while certainof the esters of Table I, for example, methyl acrylate, may serve best for the accomplishment of the reduction of grain size and the production ofa ductile, lustrous though milky deposit when used alone, such esters are not necessarily the best ones to achieve, in conjunction with utilization of the organic sulfur-containing brighteners, the production of bright mirror-like deposits over matte metal surfaces. Thus, for example, a better conjoint effect is produced through the utilization of z-methoxy ethyl acrylate in conjunction with o-benzoyl sulfimide than with methyl acrylate in conjunction with o-benzoyl sulfimide. Moreover, the 2-methoxy ethyl acrylate has the practical advantage over the methyl acrylate in that it is less volatile.

I have also found thatthe presence of free 2-methoxy ethanol or Z-phenoxy ethanol 'or the like in the baths in concentrations of about 1 to 15 grams per liter or even higher helps to brighten the medium and lower current density areas, especially when the compounds of Table II are also present with the compounds of Table I. The free Z-methoxy ethanol or similar compounds may be present in the reaction mixture resulting from the processes of preparation of the esters of such ethanol derivatives, for example, Z-methoxy ethyl acrylate, or they may be added as such to the baths.

It will be understood that, from time to time, it is necessary to replenish the bath to replace losses due to cathodic processes, to drag-out, and to other causes, in order to maintain the concentrations of the added esters, etc. in operative proportions.

When the unsaturated esters (Table I) are used without the organic sulfur compounds (Table II) in the nickel baths (especially the high sulfate type), it is often advantageous to use uch sequestering agents as trimethylamine a,ot',m"- tricarboxylic acid, ethylene diamine tetra-acetic acid, or their salts (in concentrations up to about 3 grams per liter) for their beneficial effect in the cathode film in aiding ductilization of the high current density plate especially when the pH values are between about 3.5-5.0.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. A method of electrodepositing nickel which comprises electrolyzing an aqueous acidic bath containing at leastone nickel salt selected from the group consisting of. nickelchloride, nickel sulfate, nickel fluoborate, nickel sulfamate and mixtures thereof, said bath also containing, in.

where is the acyl radical of an unsaturated aliphatic monocarboxylic acid containing not more than 6 carbon atoms and the unsaturation of which is due solely to double bonds, and X is a member selected from the group consisting of methyl, ethyl,;2-methoxyethyl, Z-ethoxyethyl, z-(p methoxyethoxy) ethy1, phenyl, and Z-phenoxyethyl,

2. A method of electrodepositing nickel in accordance with claim 1 wherein said ester is 2-methoxyethy1 acrylate. 3. A method of electrodepositing nickel in accordance with claim 1 wherein said ester is 2-ethoxyethyl acrylate. 4. A method of electrodepositing nickel in accordance with claim 1 wherein said ester is 2-(5 methoxyethoxy) ethyl acrylate. a 5. A method of electrodepositin brilliant, lustrous, ductile deposits of nickel which comprises electrolyzing an aqueous acidic bath containing at least one nickel salt selectedv from the group consisting of nickel chloride, nickel sulfate, nickel fluoborate, nickel sulfamate and mixtures thereof, said bath also containing, in solution, not more than about .5% of at least one bath-soluble ester"- having the formula: a R-(fi-OX is the acyl radical of an unsaturated aliphatic monocarboxylic acid containing not more than 6 carbon atoms and the unsaturation of which is due solely to double bonds, and X is a member selected from the group consisting of methyl, ethyl, e-methoxyethyl, 2-ethoxyethyl, 2-99 methoxyethoxy) ethyl, phenyl, and Z-phenoxyethyl, and of at least one brightener selected from the group consisting of organic sulfonamides, sulfonimides and sulfonic acids.

6. A method of electrodepositing nickel in accordance with claim 5 wherein said ester is 2-methoxyethyl acrylate.

7. A method of electrodepositing nickel in accordance with claim 5 wherein said ester is Z-ethoxyethyl acrylate.

8. A method of electrodepositing nickel in accordance with claim 5 wherein said ester is 2- (B methoxyethoxy) ethyl acrylate.

9. A bath for the electrodeposition of nickel comprising an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel chloride, nickel sulfate, nickel ,fluoborate and mixtures thereof, said bath also containing not more than about .5% of an ester having the formula:

where is the acyl radical of an unsaturated aliphatic monocarboxylic acid containing not more than 6 carbon atoms and the maturation of which is due solely to double bonds, and X is a member selected from the group consisting of methyl, ethyl, Z-methoxyethyl, 2-ethoxyethyl, 2- (p methoxyethoxy) ethyl, phenyl, and Z-phenoxyethyl.

10. A bath in accordance with claim 9, wherein said ester is methyl acrylate.

11. A bath in accordance with claim 9, wherein said ester is Z-methoxyethyl acrylate.

12. A bath in accordance with claim 9, wherein said ester is 2-(5 methoxyethoxy) ethyl acrylate.

13. A bath in accordance with claim 9, wherein said ester is 2-ethoxyethyl acrylate.

14. A bath in accordance with claim 9, wherein said ester is 2-phenoxyethyl acrylate.

15. A bath for the electrodeposition of nickel comprising an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel chloride, nickel sulfate, nickel fiuoborate' and mixtures thereof, said bath also containing not more than about .5% of an ester having the formula:

R (":-ox

where is the acyl radical of unsaturated aliphatic monocarboxylic acid containing not more than 6 carbon atoms and the unsaturation of which is due solely to double bonds, and X is a member selected from the group consisting of methyl, ethyl, 2-methoxyethyl, 2-ethoxyethyl, 2-(5 methoxyethoxy) ethyl, phenyl, and Z-phenoxyethyl, and at least one brightener selected from the group consisting of organic sulfonamides, sulfonimides and sulfonic acids.

16. A bath in accordance with claim 15, wherein said brightener is benzene sulfonamide.

17. A bath in accordance with claim 15, wherein said ester is 2-methoxyethyl acrylate.

18. A bath in accordance with claim 15, wherein said ester is 2-(p methoxyethoxy) ethyl acrylate.

19. A bath in accordance with claim 15, wherein said ester is 2-ethoxyethyl acrylate.

20. A bath in accordance with claim 15, wherein said sulfonimide is o-benzoyl sulflmide.

-21. A bath for the electrodeposition of nickel comprisin an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel chloride, nickel sulfate, nickel fiuoborate and mixtures thereof, said bath also containing not more than about .5% of an ester having the formula:

where is the acyl radical of an unsaturated aliphatic monocarboxylic acid containing not more than 6 carbon atoms and the unsaturation of which is due solely to double bonds, and X is a member selected from the group consisting of methyl, ethyl, Z-methoxyethyl, 2-ethoxyethyl, 2-(fi methoxyethoxy) ethyl, phenyl, and 2-phenoxyethyl, and not more than about 3 grams per liter of a sequestering agent selected from the group consisting of ethylene diamine tetra-acetic acid, trimethyl amine a,a',a-tricarboxylic acid and their salts.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,389,179 Brown Nov. 20, 1945 2,466,677 Brown Apr. 12, 1949 2,523,161 Struyk et a1 Sept. 19, 1950 

1. A METHOD OF ELECTRODEPOSITING NICKEL WHICH COMPRISES ELECTROLYZING AN AQUEOUS ACIDIC BATH CONTAINING AT LEAST ONE NICKEL SALT SELECTED FROM THE GROUP CONSISTING OF NICKEL CHLORIDE, NICKEL SULFATE, NICKEL FLUOBORATE, NICKEL SULFAMATE AND MIXTURES THEREOF, SAID BATH ALSO CONTAINING, IN SOLUTION, NOT MORE THAN ABOUT .5% OF AT LEAST ONE BATH-SOLUBLE ESTER HAVING THE FORMULA: 